President Bush has indicated his determination to press ahead with a missile defence shield and maintain his opposition to the Kyoto agreement on reducing greenhouse gases.

It's about time a leader stepped forward and made it clear that Russia is not the enemy... It's a new day

George Bush

Environmental issues are likely to feature prominently when the president flies to London on Wednesday before going on to the G8 summit of major industrialised countries in Genoa.

Mr Bush told the BBC he had to deal with America's energy crisis at the same time as developing an environmental strategy.

On the eve of his departure, Mr Bush also delivered a speech at the World Bank urging the organisation to provide more grants to poorer countries rather than loans.

Mr Bush told the World Bank the move would be a great step forward

The president said such a move would be a great step forward in providing human needs such as education, health services and water supplies.

World Bank officials estimate that if the proposal was adopted, the US would have to roughly double its contribution to the bank's funds.

The US currently contributes $803m a year

Kyoto dismissed

On Kyoto, the Mr Bush has simply dismissed the existing protocol as not a proper way to proceed.

"I've got an obligation to the working people of America", he said, "to pursue a policy that protects the environment but also promotes economic growth."

Last weekend saw the first successful test of the interception system

In defending his ambitious plan for a missile defence shield, the president was animated and adamant.

"It's about time a leader stepped forward and made it clear that Russia is not the enemy, and therefore we shouldn't have a treaty that was written to clarify that status ... it's a new day," said Mr Bush.

Despite such words, the planned shield, which would break the terms of the 1972 Anti-Ballistic Missile Treaty, is viewed with scepticism among Nato allies and deep suspicion by Moscow and Beijing.

Difficult trip

The BBC's Stephen Sackur, who interviewed the president, says it seems no amount of global opposition or scepticism is going to stop Mr Bush making a fundamental change to the strategic balance.

The president said he was looking forward to renewing his friendship with Tony Blair and to visiting the Queen at Buckingham Palace.

However, our correspondent says even before his departure, it is clear this trip is going to be another round of difficult transatlantic diplomacy.